1. Field of the Invention
The present invention relates to an apparatus for the optoelectronic, or electrical, control of a flame cutting machine and, more specifically, to a flame cutting machine that employs light wavelength sensitive elements for monitoring and controlling several different phases of a flame cutting process.
2. Background Information
A method to continuously control a gas, or flame, cutting process by the employment of a photoelectric element directed onto the cutting flame, is known. The method monitors whether a change of the brightness of a portion of the gas cutting flame, including the oxidizing reaction, occurs through the monitoring of the photoelectric element. That method is disclosed in German Auslegeschrift No. 2,203,194. With that method, the gas cutting process is adjusted by automatically controlling the cutting speed and by stopping the cutting apparatus if, for example, a misfire occurs.
To implement that method, the photoelectric element is positioned at an upper end of a burner. The flame is monitored through a central bore provided for the cutting oxygen in the burner and through a channel provided in the cutting nozzle of the burner. The photoelectric element is directed onto the brightly glowing portion of the flame when positioned in this manner.
The cutting speed is continuously controlled by detecting whether a change of the output voltage of the photoelectric element occurs within a predetermined range. However, with this apparatus and method, only one criterion, i.e the change of the brightness of the portion of the oxidizing reaction gas cutting flame, is detected to control the cutting speed and to stop the gas cutting process in case of misfire.
In order to increase in the efficiency of the method, or process and to save material, it has been proposed to separately record and assess the temperature of the flame, the ignition temperature of the material to be cut and the temperature of the front cutting face. To accomplish that, a signal corresponding to the flame temperature is analyzed for the control of the gas flow, a signal of the ignition temperature of the metal is analyzed for the control of the cutting oxygen and for the movement of the beam and a signal of the temperature of the front cutting face is analyzed for determining when an interruption of the cutting process should occur
In an attempt to accomplish this process by opto-electronic control, a photo generator or photo cells, are positioned in the burner that has a channel for cutting oxygen. The photo generator comprises three individual photoelements, or photo cells, that independently are connected with a computing device. The photoelements exhibit different spectral sensitivity. A first photoelement is connected with a control system for the flow of the gas and for a co-ordinate drive system. The optical characteristic, or sensitivity, of that photoelement are selected to correspond to and monitor the temperature of the flame.
A second photoelement is connected with a system for controlling the flow of the cutting oxygen and for controlling the co-ordinate drive system. The optical characteristics of the second photoelement are selected to correspond to and monitor the ignition temperature of the metal, or material, to be cut.
A third photoelement is, also, connected with the system for controlling the flow of the cutting oxygen and for controlling the co-ordinate drive system. The optical characteristics of the third photoelement are selected to correspond to and monitor the temperature of the front cutting face of the metal, or material, to be cut.
The purpose of individually selecting the optical characteristics of the three photoelements is to maximize the sensitivity thereof in relation to the optical phenomenon detected by each photoelement. In other words, the characteristics of each photoelement are individually chosen to correspond to the characteristics of the item being monitored. Such characteristics may include color or wavelength of light, intensity of light and the spectrum of light.
However, an analysis of the amplitude of the output of the signals of the photoelements is performed, i.e. as to the brightness of the flame, the workpiece, or the cutting face, within the spectral sensitivity range of each, respective photoelement. Further, the output of each photoelement is analyzed independently from the output of the other photoelements.
The analysis of the amplitudes of the output signals of the photoelements does not, however, provide unambiguous evidence regarding, for example, the flame being monitored when the attainment of the ignition temperature occurs or when the attainment of the cutting of the burner occurs, since the amplitudes of the output signals of the photoelements are subject to strong interferences. Changes, due to interference, of the amplitude levels of the output of the photoelements occur, for example, when a nozzle is changed, when the height of the burner above the workpiece is changed and when the cutting speed is varied.